Remote sensing techniques are a useful tool for continuous observation of the Earth at global scale.However,products derived from remote sensing data require a rigorous validation using in situ data.Moderate Resolutio...Remote sensing techniques are a useful tool for continuous observation of the Earth at global scale.However,products derived from remote sensing data require a rigorous validation using in situ data.Moderate Resolution Imaging Spectroradiometer(MODIS)is not really a sounding instrument,but it does have 16 infrared bands(bands 20-36 covering the spectral range from 3μm to 14μm)that allow the retrieval of temperature and moisture profiles as well as total column integrated magnitudes.In this paper we show the results obtained in the evaluation of MOD07 daytime and nighttime products over the Iberian Peninsula during the decade from 2000 to 2010 using nine radiosonde stations.Although MODIS limitations in comparison with other sounding instruments,the validation provided satisfactory results,with bias(MOD07 minus radiosonde)<0.3 cm and a standard deviation of 0.5 cm for the total column water vapor,and bias around 1 K on average with standard deviations between 2 K and 3 K for air temperature at different pressure levels.On average,bias was positive and below 2 K with standard deviations around 5 K for the dew point temperature case.Large errors were found in this case for pressure levels higher than 50 hPa.展开更多
Remote sensing and climate digital products have become increasingly available in recent years.Access to these products has favored a variety of Digital Earth studies,such as the analysis of the impact of global warmi...Remote sensing and climate digital products have become increasingly available in recent years.Access to these products has favored a variety of Digital Earth studies,such as the analysis of the impact of global warming over different biomes.The study of the Amazon forest response to drought has recently received particular attention from the scientific community due to the occurrence of extreme droughts and anomalous warming over the last decade.This paper focuses on the differences observed between surface thermal anomalies obtained from remote sensing moderate resolution imaging spectroradiometer(MODIS)and climatic(ERA-Interim)monthly products over the Amazon forest.With a few exceptions,results show that the spatial pattern of standardized anomalies is similar for both products.In terms of absolute anomalies,the differences between the two products show a bias near to zero with a standard deviation of around 0.2 K,although the differences can be up to 1 K over particular regions and months.Despite this general agreement,the proper filtering of MODIS daily values in order to construct a new monthly product showed a dramatic reduction in the number of reliable pixels during the rainy season,while for the dry season this reduction is only seen in Northern Amazonia.展开更多
This work presents the preliminary results of the first field calibration campaign performed in the Atacama Desert,Chile,between the 18 and 22 August 2014,called the Atacama Field Campaign(ATAFIC 2014).In situ measure...This work presents the preliminary results of the first field calibration campaign performed in the Atacama Desert,Chile,between the 18 and 22 August 2014,called the Atacama Field Campaign(ATAFIC 2014).In situ measurements were performed in order to spectrally characterize the surface reflectance spectra between 0.3 and 2.5μm,radiometric temperature(8.0–14.0μm)and atmospheric measurements.A soil sample was collected and analyzed using Fourier Transform Infrared Spectroscopy and X-Ray Diffraction techniques to characterize the surface reflectance spectra and mineralogical composition,respectively.ASTER land surface emissivity in addition to GOES,MODIS and Landsat-8 land surface temperature(LST)were also used.Results showed that the spectral features of the Atacama soil and the characteristics of this geographical zone,which is featured as the most hyper-arid and cloudless place in the world,make this area a potential target for surface reflectance characterization.Day and night LST comparison between field and remote sensing data are lower than 2 K and the Root Mean Square Error for land surface emissivity is close to 2%.This work opens the possibilities to consider the Atacama Desert as a reference target for calibration and validation activities for earth observation missions’purposes.展开更多
基金We acknowledge funding from European Union[CEOP-AEGIS,project FP7-ENV-2007-1 Proposal No.212921]the Ministerio de Economía y Competitividad[EODIX,project AYA2008-0595-C04-01+1 种基金CEOS-Spain,project AYA2011-29334-C02-01]the Universitat de València[grant number PRECOM13-115366].
文摘Remote sensing techniques are a useful tool for continuous observation of the Earth at global scale.However,products derived from remote sensing data require a rigorous validation using in situ data.Moderate Resolution Imaging Spectroradiometer(MODIS)is not really a sounding instrument,but it does have 16 infrared bands(bands 20-36 covering the spectral range from 3μm to 14μm)that allow the retrieval of temperature and moisture profiles as well as total column integrated magnitudes.In this paper we show the results obtained in the evaluation of MOD07 daytime and nighttime products over the Iberian Peninsula during the decade from 2000 to 2010 using nine radiosonde stations.Although MODIS limitations in comparison with other sounding instruments,the validation provided satisfactory results,with bias(MOD07 minus radiosonde)<0.3 cm and a standard deviation of 0.5 cm for the total column water vapor,and bias around 1 K on average with standard deviations between 2 K and 3 K for air temperature at different pressure levels.On average,bias was positive and below 2 K with standard deviations around 5 K for the dew point temperature case.Large errors were found in this case for pressure levels higher than 50 hPa.
基金funded by the University of Valencia[UV-INV-PRECOMP13-115366]Ministerio de Ciencia e Innovación[CEOS-Spain,AYA2011-29334-C02-01],CONICYT[Fondecyt Iniciacion–1130359]the University of Chile[Ayuda U Viajes,VID-Uchile 2014–2015].
文摘Remote sensing and climate digital products have become increasingly available in recent years.Access to these products has favored a variety of Digital Earth studies,such as the analysis of the impact of global warming over different biomes.The study of the Amazon forest response to drought has recently received particular attention from the scientific community due to the occurrence of extreme droughts and anomalous warming over the last decade.This paper focuses on the differences observed between surface thermal anomalies obtained from remote sensing moderate resolution imaging spectroradiometer(MODIS)and climatic(ERA-Interim)monthly products over the Amazon forest.With a few exceptions,results show that the spatial pattern of standardized anomalies is similar for both products.In terms of absolute anomalies,the differences between the two products show a bias near to zero with a standard deviation of around 0.2 K,although the differences can be up to 1 K over particular regions and months.Despite this general agreement,the proper filtering of MODIS daily values in order to construct a new monthly product showed a dramatic reduction in the number of reliable pixels during the rainy season,while for the dry season this reduction is only seen in Northern Amazonia.
基金partially funded by Fondecyt Initial[CONICYT/ref-11130359]The authors would also like to thank CNPq and CAPES for the scholarship given to Ms.Cibele T.Pinto and its research financial support.
文摘This work presents the preliminary results of the first field calibration campaign performed in the Atacama Desert,Chile,between the 18 and 22 August 2014,called the Atacama Field Campaign(ATAFIC 2014).In situ measurements were performed in order to spectrally characterize the surface reflectance spectra between 0.3 and 2.5μm,radiometric temperature(8.0–14.0μm)and atmospheric measurements.A soil sample was collected and analyzed using Fourier Transform Infrared Spectroscopy and X-Ray Diffraction techniques to characterize the surface reflectance spectra and mineralogical composition,respectively.ASTER land surface emissivity in addition to GOES,MODIS and Landsat-8 land surface temperature(LST)were also used.Results showed that the spectral features of the Atacama soil and the characteristics of this geographical zone,which is featured as the most hyper-arid and cloudless place in the world,make this area a potential target for surface reflectance characterization.Day and night LST comparison between field and remote sensing data are lower than 2 K and the Root Mean Square Error for land surface emissivity is close to 2%.This work opens the possibilities to consider the Atacama Desert as a reference target for calibration and validation activities for earth observation missions’purposes.
